20190752 Ver 4_Chemours Stream Flow-through Cell Project NC SHPO Cover Letter 08-12-2020 draft_20200813

Date
Renee Gledhill -Earley
State Historic Preservation Office
4617 Mail Service Center
Raleigh, NC 27699-4617
RE: Section 106 Consultation for the Chemours — Stream Flow -through Cell Project, Chemours
Fayetteville Works, Bladen County, North Carolina
Dear Ms. Gledhill -Earley,
On February 25, 2019, the North Carolina Superior Court for Bladen County entered a Consent
Order (CO) among The Chemours Company FC, LLC (Chemours) and the State of NC and Cape
Fear River Watch to address discharges of perfluoroalkyl and polyfluoroalkyl substances (PFAS)
at the Chemours Fayetteville Works. Among other things, the CO required Chemours to develop
a remedial plan for reducing PFAS loading from Chemours Fayetteville Work Facility to the Cape
Fear River. Chemours is developing four flow -through cell instream treatment facilities to treat
the water prior to discharge into the Cape Fear River. The project area is shown on Figure 1.
A preconstruction notification (PCN) for Nationwide Permit 38 (Cleanup of Hazardous and Toxic
Waste) is being prepared to comply with Section 404/401 of the Clean Water Act. Since a U.S.
Army Corps of Engineers (USACE) permit under Section 404 of the Clean Waters Act will be
obtained, Section 106 consultation is required.
Release of per- and polyfluoroalkyl substances (PFAS) from the Chemours Company FC, LLC
Fayetteville Works Facility to the Cape Fear River are derived from impacted groundwater
discharging to surface water as seeps. Four groundwater seeps, identified as Seeps A, B, C and
D, are located above the Cape Fear River water level on the bluff face from the facility and
discharge into the Cape Fear River. The locations of Seeps A, B, C, and D are shown on Figure 2.
The treatment flow -through cells will involve the installation of an in -stream system to remove
PFAS contaminants from the surface water at the seeps. Chemours is developing four (4) flow -
through cell in -stream treatment facilities to treat the water prior to discharge, beginning with a
pilot study at Seep C. The proposed Consent Order Addendum currently in negotiation requires
the Seep C pilot to be operational (construction complete) by November 16, 2020. To meet this
schedule, mobilization for construction is intended no later than October 5, 2020. The remaining
three seep flow -through cells will be constructed from February through April 2021. Chemours
intends to submit optimized designs for the remaining seeps (A, B, D) by December 31, 2020
after approximately one month of pilot operation. Chemours will construct four instream flow -
through cell structures in four unnamed tributaries east of the Fayetteville Works Facility in the
Cape Fear River floodplain. Release of per- and polyfluoroalkyl substances (PFAS) from the
Chemours Company FC, LLC Fayetteville Works Facility to the Cape Fear River are derived
from impacted groundwater discharging to surface water as seeps. The proposed interim
remedy for the seeps (flow -through cells) will construct in -stream filter beds to remove PFAS
from the seeps prior to discharge to the river. An earthen dam will impound water

(approximately 6 feet in total height) to provide hydraulic head to allow for treatment with
granular activated carbon (GAC) filter beds. Impounded water will flow through an inlet weir into
a series of concrete basins to hydraulically control surface flow over vertically oriented GAC
beds. Water will flow via gravity drainage through the GAC beds and PFAS compounds will sorb
to the media. Effluent water will collect in a stilling basin, where it will then discharge back into
the existing seep channel. The in -stream structures will be placed generally about 200 feet
upland from the confluence with the River. Influent and effluent samples will be collected to
monitor the PFAS removal efficiency. GAC media will be periodically replaced.
The flow -through cell at Seep C is being designed and constructed as a pilot study, and results
from its operation will inform the design, optimization, and installation of flow -through cells at the
remaining seeps. Design of the flow -through cells at Seeps A, B, and D, are anticipated to be
completed by the end of 2020. It is anticipated that the flow -through cells will operate for
approximately two to three years, at which point a long-term remedy for seeps and groundwater
will be constructed. This long-term remedy is anticipated to withdraw sufficient groundwater via
pumping wells such that the seep baseflow to the four flow -through cells is reduced, and the flow -
through cells can be taken out of service.
Please find attached the North Carolina State Historic Preservation Office Section 106 Project
Review packet for your review and comment. The project area is approximately 55 acres.
Archival research, a walk-through field reconnaissance, and a site files search with your office
was previously conducted. Although no cultural resources investigations have been conducted
on the proposed project area, regional studies indicate that the probability for encountering intact
prehistoric or historic archaeological sites is considered low.
On behalf of USACE, I have determined that this undertaking will have no effect on historic
properties. In accordance with Section 306108 (formerly Section 106) of the National Historic
Preservation Act and its implementing regulations, 36 CFR Part 800, USACE requests the North
Carolina State Historic Preservation Officer's (SHPO) concur with this determination.
Thank you for your assistance in this matter and a prompt reply would be greatly appreciated.
Please provide written comments to USACE within 30 days of receipt of this letter. If no written
response is received within 30 calendar days, it will be assumed that your office concurs with the
USACE's finding of no historic properties affected.
Sincerely,
USACE Signature Block
Attachment- Figure 1 and 2 — Project Maps

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Figure 1. Chemours Flow -through Cells Project Area (USGS Duart Quadrangle, Bladen County, North Carolina).

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Figure 2. Location Map, Seeps A, B, C, and D, Chemours- Stream Flow -through Cell Project